This application claims the priority of German Patent Application No. 197 46 570.6, filed Oct. 22, 1997.
The invention relates to a method and a device for extensive traffic situation monitoring of a road network on which vehicles can travel. This can be in particular a street network, but it is also possible to have traffic situation monitoring of a rail network or a shipping network.
The prior art patent document WO 96/13733 describes a method for monitoring shipping at sea with detection of oil pollution and icebergs, as well as possible collision risks between ships and/or between ships and icebergs. In this method, oil pollution and icebergs on the surface of the sea are observed and detected by satellite-supported SAR (synthetic aperture radar) microwave sensors. At the same time, a position-determining device is mounted on each vessel that determines the current position of the ship in question and transmits the corresponding position information to whatever satellite is within the visibility range of this position-determining device at that point in time. The satellites then transmit the data on position and size of any detected oil pollution and of any icebergs that are detected as well as the current ship position data received from the vessels to a land-based evaluation center. The evaluation center evaluates these data to identify the cause of the oil pollution and to determine potential collision risks between ships or between a ship and icebergs, and issues a corresponding warning message via the satellites to the ships in question if necessary.
It is known that position determination of vehicles can be performed with the support of a satellite-supported navigation system, for example the GPS (global positioning system). A suitable receiver is installed in the vehicle for this purpose. The receiver receives the position-determination signals transmitted from satellites and evaluates them to determine the position of the vehicle; see for example German Patent document DE 196 21 917 A1.
To monitor the traffic situation, especially in road traffic, infrastructure-supported systems are frequently employed today in which traffic situation data are gathered by measuring devices such as induction coils mounted in the road and fed to a center where they are checked for malfunctions using special algorithms. This requires a considerable expense for the infrastructure along the road network, since the measuring devices must be mounted along every road with spaces between them that are sufficiently small to obtain the desired accuracy of the traffic situation monitoring. In addition, this procedure is very inflexible when it comes to making changes in the road network.
In an infrastructure-supported traffic monitoring system disclosed in German Patent document DE 41 28 312 A1, video cameras are positioned for observing traffic at traffic intersections or at other trouble-prone locations in the traffic network. The pictures taken in this way are analyzed by an associated image processing system using a suitable pattern recognition method specific for vehicle models for the presence of movements in order to determine the number of vehicles of each model that pass the location of an individual video camera.
In another method practiced at the present time, the traffic situation data are gathered manually, with monitoring personnel traveling on the road network in vehicles or flying in helicopters over portions of the road network that are known to be prone to problems, and reporting traffic problems by radio or the like to a center. This method makes it necessary to confirm problem reports before the problem report is issued by radio for example. Because of the relatively long delay this method entails, frequently a problem that has been announced is no longer present, or a problem that has already developed has not yet been announced to drivers.
Recently, the use of specially equipped test vehicles moving in traffic has been proposed as another method for monitoring the traffic situation on the road. These vehicles are designed for determining the local traffic flow encountered by the test vehicle in question and for passing on corresponding traffic flow data. By using a suitable large number of these test vehicles, also called "floating cars," a realistic picture of the extensive traffic situation in the road network can be supplied from the individual local traffic flow data. This type of random sampling for monitoring the traffic situation however is theoretically unable to guarantee that the traffic situation at every point in space and at every point in time on the road network can be detected accurately, and also requires a corresponding expense for specially equipping a large number of test vehicles.
There is therefore needed a method and a device of the above-mentioned type which can solve the above problems by performing reliable extensive traffic situation monitoring at comparatively low expense.
The present invention solves these problems by providing a method for extensive traffic situation monitoring of a road network on which vehicles travel, characterized in that remote photographs are taken of the area to be monitored by aircraft;
the images that are taken are subjected to an image-processing procedure to localize the roads in the road network and to detect vehicles on them; and conclusions about the current traffic situation are drawn from the vehicles recognized, as well as a device for extensive traffic situation monitoring of a road network on which vehicles travel, with one or more aircraft that are equipped with an image-recording system for recording images of the part of the Earth's surface on which road network is located, and an evaluation center that receives image-related data from the aircraft and uses this data to draw conclusions about the traffic situation, wherein the evaluation center includes an image-processing system to which the image data from the images recorded by the aircraft are transmitted and which localizes the roads in the road network in the images that are taken, and recognizes vehicles that are on the road network, and draws conclusions about the traffic situation from the vehicles recognized by the image-processing system.
In the method according to the present invention, pictures of an area to be monitored, in which the road network is located, are taken from a distance by aircraft, especially satellites or airplanes. The pictures received are subjected to automated image processing to localize the roads of the road network in each image and to recognize vehicles on the localized roads. With the aid of the detected vehicle, conclusions are then drawn regarding the traffic situation at the moment.
Advantageously, no roadside infrastructure and no special equipment in the vehicles are required for this method. In addition, satellites and airplanes with which remote photographs of the surface of the ground can be made in the manner required are already known. In addition, automated image-processing techniques for evaluating such images are already in use. Image-processing therefore merely needs to be designed for localization of the roads in question and detection of the vehicles on them, which is possible for the individual skilled in the art without considerable additional expense, on the basis of a conventional image-processing system. The method can thus be implemented relatively inexpensively. The speed with which the traffic situation can be determined reliably by this method, as well as the extensiveness of the determination, in other words at all points in the road network and at any point in time, is advantageous. The method can be extended quickly and simply to new areas of the road network.
In a preferred embodiment of the method according to the invention, the localization of the roads in the pictures taken is performed with the aid of a conventional map-matching method with superimposed vector maps, so that the routes of interest can be reliably determined.
In a further preferred embodiment of the method according to the invention, images of the area to be monitored are taken using various forms of imaging radiation. Depending on the weather conditions, it may be possible to temporarily get better pictures with one type of radiation than with another type of radiation. Then, the most suitable of the pictures can be selected for further evaluation, so that traffic situation monitoring can be performed as independently as possible of the weather conditions while the reliability remains constant.
In another preferred embodiment of the method according to the invention, traffic situation monitoring includes a traffic situation-dependent estimate of travel times between a starting location that can be specified and a target location that can likewise be specified, with the estimate being performed on the basis of vehicles that are on the road network and are detected by the method.
In yet another preferred embodiment of the method according to the invention, images are taken repetitively at predeterminable time intervals of the area to be monitored. On the basis of vehicles that are recognized in the images that are taken successively, the development and/or movement of a traffic problem can be determined, in other words, the dynamics of a given traffic problem can be monitored.
In still another preferred embodiment of the method according to the invention, the spatial position of the detected vehicle is determined by simply recognizing the location where a vehicle is on the road at a given moment. A traffic problem, for example in the form of a traffic accident, is then determined to have occurred from abnormal vehicle positions, for example from the presence of one or more vehicles that are located crosswise to the road or are tipped over.
The device according to the invention is suitable for performing the method according to the invention, for which purpose it has one or more aircraft equipped with image-recording systems for taking pictures of the Earth's surface and for transmitting corresponding image data, as well as an evaluation center that is preferably land-based. The evaluation center incorporates a suitably designed image-processing system for locating the roads in the road network and for recognizing the vehicles on them. The evaluation center also has required conventional means in order to draw conclusions about the traffic situation on the basis of the vehicles that are recognized on the road network. On the other hand, the vehicle does not require any means along the road or aboard the vehicles for monitoring the traffic situation.
The device according to the invention advantageously incorporates a travel-time estimating device that is especially suited for performing the method in which travel times are estimated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.